Such a device is basically known from DE 20 2004 003 646 of the present inventor, wherein this targeting device has shown precise control in many surgical or stereotactic interventions on or in the human body. Especially by the use of modern computer technologies, such as computer tomography (CT) or magnetic resonance imaging, it is possible to precisely define the necessary insertion points, entrance depths and entrance directions of medical instruments, so that a target device for guiding these instruments has to comply with the increased accuracy. By means of such CT patient data and parameters an instrument can then be brought to the defined target point on or in the body. A special application with radio frequency ablation (RFA) is described in “chemiereport.at 7/11, p. 42.
Essential features of such targeting devices for guiding medical instruments are high accuracy and quick reproducibility. However, the stereotactic accuracy is reduced with repeated operations, as the device has to be changed for each instrument. Many treatments require different needle diameters, so that not only the needle sleeves must be replaced, but the target axis may shift according to puncture needles with different diameters and must therefore be re-adjusted. This also applies for the radiation therapy, in which so-called pins or seeds are directly delivered into the tumor tissue to be irradiated. Thus, it is possible to achieve significant improvements in this area by computer-based navigation systems, wherein the position of the needle tip in or on the body is displayed on the screen instead of the location of the probe tip. The request for a fast and easy reproducibility still requires improvements to the targeting device in order to maintain the exact adjustment in all spatial axes.
The above-mentioned document (or the corresponding WO 2005/084565) discloses a precise and variable guide for such medical instruments (including needles) wherein actuators, arranged above each other, permit remote control in an advantageous way. This instrument guide holder has two joints, particularly ball heads formed at the front ends of adjusting arms, which are, however, relatively difficult to change, especially when different needle sizes are required. In addition, a plurality of guide sleeves (“inserts”) are needed for adapting to the respective needle diameters, being cost-increasing. Also, depending on the manufacturer different tolerances exist, so that the accuracy and sensitivity of needle advancement may suffer by slightly “sticking”. This also applies for a rapid release of the needle (f. i. when the patient becomes restless), such that the needle or the instrument must be quickly retreated out of the holder.